Again, no auth.net abr but the EPN gateway I was using would assign a "recur id". I attached this to the invoice my post back script created for reference. Everyt time a postback was received from a recur execution, my post back script would create an "invoice" for either a successful renew or a failed renew, either or. On that system when the recur failed the recur setup was autmatically cancelled so when the user updated their info a new recur would have to be set up, and that new assigned recur id would be attched to the invoice generated at the time of renewal.
The invoices were obviously attached to subscriber accounts. Things I would keep in the inovice records would be a unique invoice id, txresult, recurid, subscriber id, date / time and amount.
The administrator panel was able to view / print / email invoices as well, I had the system always email the customer with a copy of the invoice when generated.
It was a pretty advanced system I wrote for this, took a lot of time and figuring out how to handle all this stuff, much like what you're dealing with right now so I feel your pain.